Chemotherapy modalities and immune condition of the host

It is clear that it is possible to improve the immune condition of the host and to increase its immunological reactivity by employing a range of modalities. These may involve nonspecific immunostimulation of the host, active or passive immunization, adoptive chemotherapy, alteration of tumor cell antigenicity or other types of approaches. New agents may be sought that will serve as immunostimulants or that may prevent immunosuppression by tumor growth or by chemotherapeutic agents. New analogs of the known antitumor agents may be examined to determine whether they are less immunosuppressant than the parent drug. Any means leading to the net improvement of the immune status of the host may result in diminished drug toxicity for the host, increased antitumor response, and augmentation of immunochemotherapy.

Inhaled isotretinoin (13-cis retinoic acid) is an effective lung cancer chemopreventive agent in A/J mice at low doses: a pilot study

In previously treated head-and-neck cancer patients, p.o. administered isotretinoin (13-cis retinoic acid) reduced the occurrence of second aerodigestive tumors, including lung tumors, but side effects made chronic therapy problematic. We reasoned that inhaled isotretinoin might provide sufficient drug to the target cells for efficacy while avoiding systemic toxicity, and we proceeded with the pilot study reported here. Male A/J mice were given single i.p. doses of urethane, a common experimental lung carcinogen, or benzo[a]pyrene (BaP) or 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), putative major carcinogens in tobacco smoke. The following day, exposures to isotretinoin aerosols for 45 min daily at 1.3, 20.7, or 481 microg/l were initiated. After 2 weeks, the high dose caused severe toxicity on the snout skin, necessitating a reduction of dose frequency to twice a week. As a precaution, the mid dose was reduced to three exposures per week. The weekly total deposited doses after the dose frequency reductions were calculated to be 0.24, 1.6, and 24.9 mg/kg for the low, mid, and high doses, of which 16% was estimated to be deposited in the lungs. The weekly deposited pulmonary drug doses were calculated to be 0.01, 0.07, and 1.1% of a previously reported ineffective oral dose in urethane-treated A/J mice. After 10-16 weeks, mice were sacrificed to count areas of pulmonary hyperplasia and adenomas. For all carcinogens, the mice exposed to the high isotretinoin dose showed reductions of tumor multiplicity ranging from 56 to 80% (P < 0.005). The mid dose was associated with reductions of tumor multiplicity by 67 and 88% (P < 0.005) in BaP- and NNK-treated mice, respectively, and was tolerated until approximately 12 weeks, when both these and the high-dose mice began losing weight. The low-dose mice had nonsignificant reductions of 30% (P < 0.13) and 16% (P < 0.30) for BaP- and NNK-treated mice, respectively without any evidence of side effects. For BaP- and NNK-treated mice, numbers of hyperplastic areas directly correlated to dose level and inversely to tumor number, suggesting arrested progression. Inhaled mid-dose isotretinoin caused up-regulation of lung tissue nuclear retinoic acid receptors (RARs) relative to vehicle-exposed mice, RARalpha (3.9-fold vehicle), RARbeta (3.3-fold), and RARgamma (3.7-fold), suggesting that these receptors may be useful biomarkers of retinoid activity in this system. The encouraging results from this pilot study suggest that inhaled isotretinoin merits evaluation in people at high risk for lung cancer.

Intraoperative detection of occult colon cancer micrometastases using 125 I-radiolabled monoclonal antibody CC49

BACKGROUND

The detection of locally-disseminated disease is one of the principal goals of oncologic surgery. For this study, a hand-held, gamma-detecting probe was used intraoperatively to assess the extent of colorectal carcinoma in patients previously injected with radiolabeled antibody to the TAG-72 antigen (CC49); this technique is known as Radioimmunoguided Surgery (RIGS) (Neoprobe Corporation, Dublin, OH). RIGS-positive areas (i.e. those with increased signal over background) have previously been shown to contain carcinoma in a high proportion of cases. However, some RIGS-positive areas had no tumor detectable by clinical examination or routine histopathologic analysis. This study was undertaken to determine if the presence of occult metastases might account for this disparity.

METHODS

A total of 57 regional lymph nodes (LN), resected from 16 patients with primary (9) or recurrent (7) colorectal carcinoma, were studied. The patients were injected with 125I labeled CC49 murine monoclonal antibody approximately 3 weeks prior to surgery. After routine histologic evaluation, the LN were analyzed for occult metastases; paraffin sections were cut at 5 levels (50 micron apart) and were examined by histology (hematoxylin and eosin stain [H & E]) and by immunohistochemistry (IHC) with a cocktail of monoclonal antibodies to cytokeratins.

RESULTS

Fifty-seven LN were included in this study; 17 were H & E-positive (i.e., contained tumor by routine histologic examination [overt tumor]), while 40 LN were H & E-negative (i.e., no evidence of tumor after routine histologic examination). Thirty-nine LN were RIGS-positive, but only 14 of these were H & E-positive. Of the 25 RIGS-positive/H & E-negative LN, 10 (40%) demonstrated the presence of occult metastases after serial section/IHC analysis. Thus, a total of 27 LN contained metastatic carcinoma (17 overt, 10 occult); routine histologic analysis was able to identify tumor in only 17 of these 27 LN (63%), while the probe signaled the presence of tumor in 24 of these LN (89%). None of the RIGS-negative/H & E-negative LN were found to have occult metastases (0/15). Specific immunoreactivity with CC49 antibody was observed in 5 of 15 RIGS-positive/H & E-negative LN in which no tumor could be identified by any method (histopathology or IHC. CC49 immunoreactivity was not observed in 15 RIGS-negative/H & E-negative LN.

CONCLUSIONS

The finding of a RIGS-positive LN had a significant association with the presence of tumor cells (P < 0.05). In this study, the RIGS procedure was more sensitive than clinical or histopathologic examination in detecting the regional spread of a tumor. Furthermore, in LN that showed no evidence of tumor by routine histopathologic examination, a positive RIGS reading was significantly associated with the presence of occult LN metastases (P < 0.01). This study is the first to demonstrate the detection of histologically occult tumor by a remote imaging device. RIGS assessment is a highly sensitive method for detecting occult tumor deposits, and may guide therapeutic intervention in patients with colorectal carcinoma.

The significance of intraoperative periportal lymph node metastasis identification in patients with colorectal carcinoma

BACKGROUND

Nine patients who underwent Radioimmunoguided Surgery (RIGS) (Neoprobe Corporation, Dublin, OH) procedures for colorectal cancer were found to have disease recurrence in the periportal area. This led to a retrospective study to determine whether periportal lymph node involvement could have been predicted intraoperatively for these patients.

METHODS

One hundred twenty-four patients underwent second-look RIGS for recurrent colon and rectal cancer from 1986 to 1992. The monoclonal antibody (MAb) B72.3 was administered as the carrier agent to 87 patients and the CC49 second-generation MAb was administered to 37 patients. Both MAbs were radiolabeled with Iodine-125.

RESULTS

Periportal lymph nodes with RIGS-positive tissue were found in 47 (38%) patients, hematoxylin and eosin-positive lymph nodes were found in 13 of 47, and in further immunohistochemical studies performed for 31 of the remaining 34 patients, positive lymph nodes were found in 8, resulting in an incidence of 48% (21/44). A critical review of the nine patients' charts who later presented with a tumor mass in the periportal area demonstrated intraoperative gamma-detecting probe counts in ratios three to five times that of the normal adjacent tissues in the periportal area at the time of first exploration. Probe-directed biopsy was reported to be histologically negative for tumor in these patients, and, thus, the surgeon proceeded assuming the periportal area to be negative. A retrospective study of the periportal lymph nodes of these patients using cytokeratin immunohistochemical analysis identified tumor in five (56%).

CONCLUSIONS

These findings suggest that the RIGS system may be a valuable method of intraoperative prediction and detection of periportal lymph node metastasis.

Comparative immunotoxicity of 2,2'-dichlorodiethyl sulfide and cyclophosphamide: evaluation of L1210 tumor cell resistance, cell-mediated immunity, and humoral immunity

The immunotoxicity of 2,2'-dichlorodiethyl sulfide (sulfur mustard, SM), on humoral and cell-mediated immunity was compared with that of the nitrogen mustard 2-[bis(2-chloroethyl)amino]tetrahydro-2H-1,3,2-oxazophosphorine 2-oxide (cyclophosphamide, CP). SM and CP had similar effects on thymic and splenic weights, spleen cell number, and the formation of antibody producing cells to sheep red blood cells (sRBC) when examined 5 days after exposure, but differed in their effects on body weights. Although there were no differences in the delayed hypersensitivity response to keyhole limpet hemocyanin, CP and SM had different effects in the L1210 tumor cell allograft rejection assay. CP, but not SM, decreased the 28 day survival rate of allogeneic mice exposed to a sublethal L1210 tumor challenge. The differing effects on survival to the L1210 tumor challenge could not be attributed to a direct cytotoxic effect of SM on the L1210 tumor cells as SM did not increase the survival rate or median survival time of syngeneic mice exposed to a lethal L1210 tumor cell challenge. In summary, SM and CP had immunosuppressive effects in the humoral immune assay. Although neither compound suppressed the delayed hypersensitivity response, CP was found to suppress host resistance to L1210 tumor cells.

Advantage of dose fractionation in monoclonal antibody-targeted radioimmunotherapy

Monoclonal antibody (MAb) B72.3 IgG was radiolabeled with 131I and administered to female athymic NCr-nu mice bearing the LS-174T human colon adenocarcinoma xenograft to determine if fractionation of MAb dose had any advantage in tumor therapy. In the LS-174T xenograft, only approximately 30%-60% of tumor cells express the B72.3-reactive TAG-72 antigen. The LS-174T xenograft was used to reflect the heterogeneity of the TAG-72 antigen often seen in biopsy specimens from patients. In contrast to a single 600-muCi dose of 131I-B72.3 IgG where 60% of the animals died from toxic effects, two 300-muCi doses of 131I-B72.3 IgG (total of 600 muCi) reduced or eliminated tumor growth in 90% of mice, with only 10% of the animals dying from toxic effects. Dose fractionation even permitted escalation of the dose to three doses (each 1 wk apart) of 300 muCi of 131I-B72.3 IgG (for a total of 900 muCi), resulting in even more extensive tumor reduction or elimination and minimal toxic effects. The use of an isotype-matched control MAb revealed a nonspecific component to tumor growth retardation, but the use of the specific B72.3 IgG demonstrated a much greater therapeutic effect. Tumors that had escaped MAb therapy were analyzed for expression of the B72.3-reactive TAG-72 antigen with the use of the immunoperoxidase method; they were shown to have the same antigenic phenotype as the untreated tumors. We verified tumor elimination by killing the test animals after a 7-week observation period and performing histologic examination of tumor sites. We also monitored toxic effects by histologic examination of numerous organs, including bone marrow. These studies thus demonstrate the advantage of dose fractionation of a radiolabeled MAb for tumor therapy. We anticipate that the concept of dose fractionation can be practically applied in radioimmunotherapeutic clinical trials with the development and use of recombinant-chimeric MAbs and modified constructs.

Effects of mainstream and environmental tobacco smoke on the immune system in animals and humans: a review

This review evaluates the available information on the effects of mainstream and environmental tobacco smoke on the immune system in animals and humans. The primary emphasis is on mainstream smoke since little information is available on the effects of environmental smoke. The effects of mainstream tobacco smoke on the immune system in humans and animals are similar. Animals exposed to mainstream tobacco smoke for periods of a few weeks generally exhibit a slight immunostimulation. However, subchronic and chronic exposure studies indicate that immunosuppressive changes develop. Lymphocyte proliferation in response to the mitogens PHA and LPS is decreased, suggesting compromise of cell function. Antibody production can be suppressed. Smoke-exposed animals that are challenged with metastasizing tumors or viruses have been shown to exhibit a higher incidence of tumorigenic and infectious diseases, respectively. Localized immunological changes in the lung can include reduction of bronchus-associated lymphoid tissue and immunoglobulin levels. Smoking-related changes in the peripheral immune system of humans have included elevated WBC counts, increased cytotoxic/suppressor and decreased inducer/helper T-cell numbers, slightly suppressed T-lymphocyte activity, significantly decreased natural killer cell activity, lowered circulating immunoglobin titers, except for IgE which is elevated, and increased susceptibility to infection. The effects of environmental tobacco smoke on the immune system, in contrast to mainstream tobacco smoke, have just begun to be investigated and information available in the literature, to date, is limited. Immunoreactive substances are known to be present in environmental tobacco smoke, but to date, environmental tobacco smoke has been more closely associated with irritation than sensitization. A few studies have indicated a potential for environmental smoke-induced hypersensitivity and suppression of immunoregulatory substances. In contrast, other investigators have failed to detect immunological or other biological changes associated with environmental smoke. Clearly, more research is needed to resolve these differences.

An assessment of prolonged reactivity of seven monoclonal antibodies against CX-1 tumor xenografts using a hand-held gamma-detecting probe

The biodistribution and kinetics of 7 monoclonal antibodies (MAb) with known reactivity against CX-1 tumor were examined over 21 days using a hand-held gamma-detecting probe (Neoprobe system). Twenty-eight immuno-deprived (athymic) nude mice implanted with human colon adenocarcinoma CX-1 xenografts were injected intraperitoneally with 50 microCi of 125I-labeled antibodies (4 mice/antibody). Of the 7 monoclonal antibodies, 4 were anti-CEA (MA, MB, MC, and MD), 2 were anti-TAG 72 (B72.3 NCI and B72.3 fermented) and one was anti-colorectal cancer (17-1A). Daily probe counts were recorded in duplicate over the tumor site and the contralateral nontumor site (background), and tumor-to-background (Tu/Bkg) ratios were calculated. Animals were sacrificed on day 21, and blood, heart, liver, spleen, lungs, kidneys, intestine, muscle, and the tumor were removed for gamma well counting. All antibodies identified the tumor as early as 24 h postinjection and specific tumor localization improved over time. Patterns of prolonged tumor binding varied considerably from one antibody to another, although all but one (MB) showed continuously increasing Tu/Bkg ratios. These data indicate progressive clearance of the antibodies from the background tissue and a persistence of labeled MAb activity in tumor resulting in improved tumor localization with increasing postinjection time.

Effect of dimethylsulfoxide and hexamethylene bisacetamide on the JOK-1 hairy cell leukemia derived cell line propagated in the nude mouse

The JOK-1 hairy cell leukemia derived cell line has been propagated as a subcutaneous tumor in nude mice. After the tumor had been serially transplanted for at least two successive generations, mice were treated with either dimethylsulfoxide or hexamethylene bisacetamide (HMBA). These agents have been shown to induce terminal leukemic cell differentiation in vitro. Our results indicated that these agents had an in vivo growth inhibitory effect, with HMBA exerting a dose-dependent response. Histopathological examination revealed massive areas of necrosis with no overt signs of cellular differentiation. These data suggest that in vitro inducers of differentiation may act via another mechanism in vivo.

Effects of ethylene glycol monomethyl (EGME) and monoethyl (EGEE) ethers on the immunocompetence of allogeneic and syngeneic mice bearing L1210 mouse leukemia

The effect of ethylene glycol monomethyl ether (EGME) and ethylene glycol monoethyl ether (EGEE) on cell-mediated immunity was evaluated by an allograft rejection assay. Allogeneic B6C3F1 (C57BL/6 X C3H) mice were given oral doses of 600, 1200, or 2400 mg/kg/administration of EGEE or 300, 600, 1200 mg/kg/administration of EGME on days -12 through -8 or cyclophosphamide (Cy) at 180 mg/kg by the IP route on day -1. Untreated controls were given oral doses of water on days -12 through -8 and -5 through -1. On day 0, the mice were challenged with 1 X 10(2), 3 X 10(3), and 1 X 10(5) or 3 X 10(6) L1210 cells by the IP route. Syngeneic CD2F1 (Balb/c X DBA/2) mice were challenged with 1 X 10(5) L1210 cells on day 0 and were treated on days 1 to 5 and 8 to 12 with the same dosages of EGME and EGEE used for the B6C3F1 mice. Water-treated syngeneic mice died with a median survival time (MST) of 8.0 days. There was no effect on the MST of syngeneic mice treated with either EGME or EGEE, indicating no direct antitumor effect of the compounds. All allogeneic mice receiving either water or Cy and challenged with 3 X 10(6) tumor cells, died with ascites. However, when mice were treated with EGME or EGEE and challenged with 3 X 10(6) tumor cells, no more than one animal per group died. This would indicate that there was a prophylactic action of the compounds or that the immune system was stimulated. Blood smears of allogeneic mice were made for differential counts the last day of drug dosing, the day of death where possible, and on survivors at day 43 post-tumor implantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Human brain tumor xenografts in nude mice as a chemotherapy model

Two human brain tumors which were previously established in nude mice were used to determine antitumor efficacy of various therapeutic agents. These tumors were a medulloblastoma (TE-671) and a glioma (U-251) with mass doubling times of 3.5 and 5.5 days respectively as subcutaneous implants in nude mice. Intracranial (i.c.) tumor challenge was accomplished by inoculating tissue culture-grown cells of either tumor into the right cerebral hemisphere to a depth of 3 mm. Median survival time (MST) in untreated mice with 10(5) i.c. injected TE-671 cells was approximately 30 days and 53 days in the U-251 tumor. With 2 X 10(5) U-251 tumor cells the MST was 27-31 days. Groups of mice which had been inoculated with tumor were treated with various doses and schedules of antineoplastic compounds by the i.p. route. The TE-671 tumor responded to AZQ treatment with an increase in life span (ILS) of 37% compared to untreated controls and an ILS of 30% with CCNU treatment. BCNU and PCNU were ineffective. With the U-251 tumor BCNU produced an ILS of greater than 60%, with 75% cures, greater than 112% ILS with PCNU and 49% ILS with CCNU. Neither tumor responded to procarbazine, PALA, dianhydrogalactitol, D-O-norleucine or dibromodulcitol. The U-251 tumor was treated on various schedules and doses with BCNU and found to respond well on late as well as early treatment. A new drug (rapamycin) being investigated by the NCI was found to be very effective against the U-251 tumor. This model system should prove valuable in assessing the effects of various chemotherapeutic modalities against brain tumors.

Combined modality treatment using radiation and/or chemotherapy in an athymic nude mouse-human medulloblastoma and glioblastoma xenograft model

A human medulloblastoma (BN-2) and a glioblastoma (BN-3) which were previously established in nude mice were used to determine the effect of combined modality therapy with gamma-radiation, and three chemotherapeutic agents, procarbazine, 1,4-cyclohexadiene-1,4-dicarbamic acid, 2,5-bis(1-aziridinyl)-3,6-dioxo diethylester (AZQ), and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). The tumor cells were grown in tissue culture and implanted intracranially in the right cerebral hemisphere of NIH Swiss nude mice to a depth of 3 mm. The mice were randomized, and treatment was started 3 days after tumor implantation. Procarbazine and AZQ were injected i.p. every 5 days for three treatments. BCNU was injected one time for a single treatment. Radiation was localized to the head. A 60Co unit was used for irradiation at the rate of 125 rads/min 3 days after tumor implantation. Ten experiments were performed using six to nine mice per group and different drug-radiation dose combinations. The drug dose ranged from 400 to 500 mg/kg/injection for procarbazine, 7.5 mg/kg/injection for AZQ, and 10 to 20 mg/kg/injection for BCNU. The radiation dose ranged from 320 to 1050 rads/mouse (whole head). The day of death was recorded for each animal, and the mean of each treatment group was used to calculate the percentage increase in life span (ILS) compared to the untreated control group. Chemotherapy alone produced a minimal effect, while radiation alone produced minimal effects at 320 to 640 rads with progressively positive effects at 800 and 1050 rads. When the combination treatment of the human medulloblastoma xenograft with procarbazine was used, the ILS was significantly increased in all four experiments, ranging from 25 to 41%, and was superior to single-modality treatment in all but the 1050-rad treatment, where it showed an equal effect. The combination treatment using AZQ and BCNU showed no ILS for the medulloblastoma tumor. Combination treatment of the human glioblastoma xenograft using BCNU produced significant ILSs of 105 and 119% and was superior to single-modality treatment with a drug dose of 10 mg/kg and radiation doses of 540 and 800 rads, respectively. The nude mouse-human tumor xenograft model was found to be useful for combined modality studies and should give valuable information for the experimental design of pilot Phase III clinical studies against a variety of brain tumors.

Collagenase inhibitors retarding invasion of a human tumor in nude mice

Tumor invasion has been correlated with the ability of tumor cells to produce collagenolytic enzymes which are capable of degrading normal host tissues. However, the human small cell carcinoma implanted subcutanouesly and growing progressively in athymic (nude) mice produced large quantities of collagenase but did not appear to significantly infultrate adjacent host tissue. In comparison, subcutaneously implanted murine Lewis lung tumors produced similar quantities of collagenase and were locally invasive. The human tumors were surrounded by a compact layer of fibroblast cells in a fibrous matrix. This fibrous sheath exhibited anticollagenase activity and indicated a mechanism of host tissue resistance to invasion via the formation of inhibitors to degradative enzymes produced by tumor cells.

Efficacy of 6-diazo-5-oxo-L-norleucine and N-[N-gamma-glutamyl-6-diazo-5-oxo-norleucinyl]-6-diazo-5-oxo-norleucine against experimental tumors in conventional and nude mice

The chemotherapeutic effects of 6-diazo-5-oxo-L-norleucine (DON) and N-[N-gamma-glutamyl-6-diazo-5-oxo-norleucinyl]6-diazo-5-oxo-norleucine (azotomycin) were evaluated in a spectrum of transplantable experimental tumor systems including xenografts of human tumors in athymic mice. Both drugs displayed remarkable activity against the murine leukemia L1210 and P388, the Colon Tumors C26 and C38 and the CD8F1 mammary tumor. No significant activity was observed against Lewis lung carcinoma, B16 carcinoma, B16 melanoma, and intracranial ependymoblastoma. DON and azotomycin also exhibited striking inhibitory effects on the growth of s.c. human tumor (MX-1 mammary, LX-1 lung and CX-1 and CX-2 colon) xenografts in athymic mice. With the exception of one colon xenograft (CX-1), all tumor lines were markedly responsive to both drugs. Tumor regressions below the initial tumor sizes of 100 to 300 mg, albeit temporary, were brought about by one course of treatment every 4 days for 3 doses (at optimal dose) with either drug. Although these drugs have been tested previously in the clinic and have shown only limited therapeutic effectiveness, they seem to worthy of a second and closer look in light of the recent laboratory results.

Therapy for mouse tumors and human tumor xenografts with the antitumor antibiotic AT-125

The antimetabolite antibiotic L-(alphaS,5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (AT-125) showed significant antitumor activity against L1210 and P388 mouse leukemias and the M5076 mouse ovarian tumor. Depending on the schedule of administration, increases in lifespan of greater than 100% were observed. Activity was observed after ip, oral, or sc inoculation of AT-125 in mice inoculated with L1210 by the ip route. Lewis lung carcinoma and B16 melanoma were not affected by AT-125. The compound was used to treat human tumor xenografts in athymic (nude) mice. The MX-1 mammary tumor regressed when treated with either 8 or 16 mg/kg/day for 10 days, while a dose of 32 mg/kg was toxic. On an every-4-days x 3 schedule there was a marked slowing of MX-1 tumor growth at 50, 100, and 200 mg/kg. The LX-1 lung tumor xenograft growth was slowed significantly by a dose of 32 mg/kg. Growth of colon tumors, CX-1, CX-2, and CX-3, was not affected by AT-125.

Chemotherapy of human tumor xenografts in genetically athymic mice

A series of studies were undertaken to evaluate the chemotherapeutic response to various antineoplastic drugs of human breast (MX-1) or colon (CX-2) tumor xenografts growing in genetically athymic (nude) mice. Fragments (2mm3) of either tumor type were implanted subcutaneously into the subaxillary region of NIH Swiss nude mice, and single drug therapy was started when tumors became palpable and were growing progressively. 5-Fluorouracil (5-FU) administered on a Q7DX3 schedule starting on Day 21 post tumor implantation elicited significant retardation in the growth rate of CX-2 tumor. A single treatment with methyl-CCNU induced temporary tumor regression. Against MX-1 tumor, both cyclophosphamide and melphalan induced tumor regressions with no recurrence. 5-FU slowed but did not arrest growth of MX-1 tumor. These tumor systems grown in nude mice appear to be suitable models for in vivo screening of anticancer agents that would prove clinically active.

Comparison of 5-fluorouracil and ftorafur. I. Quantitative and qualitative differences in toxicity to mice

5-Fluorouracil (5-FU) was compared to ftorafur, a fraudulent nucleoside analog which acts as a depot form of 5-FU, with respect to influence of dosage level and schedule of administration on toxicity in mice. When the drugs were administered daily and the duration of treatment was varied from a single dose to 32 daily treatments, the toxicity of 5-FU proved to be somewhat more than cumulative. On the other hand, the toxicity of ftorafur on daily treatment was less than cumulative. As a single treatment ftorafur was about half as toxic as 5-FU on an mg/kg basis. When the drugs were administered daily for 12 days the LD50 of ftorafur was about sevenfold that of 5-FU. When the drugs were administered as two treatments and the interval between the two treatments was varied from 0 to 14 days, it was found that 5-FU was considerably more toxic at an interval of 2-7 days than when two doses were administered simultaneously. Appreciable recovery of mice from the initial dose of 5-FU did not occur until sometime between 7 and 10 days. Host recovery from ftorafur toxicity was apparent by 2 days. The dose-mortality curves form both drugs were steep. The decreased toxicity with repeated treatment with ftorafur relative to 5-fu was not due to a decrease in the metabolism of ftorafur to 5-FU, which was much more extensive in mice compared to previously reported pharmacokinetic studies in other species. At equitoxic doses on a daily X 5 schedule, 5-FU and ftorafur had similar myelosuppressive activity. Ftorafur was, however, clearly less suppressive to both humoral and cell-mediated immunity than was 5-FU.

Effects of Corynebacterium parvum alone and in combination with adriamycin in experimental tumor systems

Corynebacterium parvum (C. parvum) was used in antitumor tests against four murine tumor models in B6D2F1 mice. The C. parvum was effective at all doses and schedules tested against P388 leukemia, B16 melanoma, and Lewis lung carcinoma but was ineffective against L1210 leukemia. Combination immunochemotherapy of P388 leukemia and Lewis lung carcinoma with C. parvum and adriamycin was better than either regimen alone in increasing the lifespan of mice with tumors. The results show that the effects of C. parvum are due to nonspecific stimulation of the host rather than direct cytotoxic action on tumor cells. C. parvum protected the mice when given before as well as after tumor challenge. In vitro 51Cr-release assay showed that the peritoneal cells were cytotoxic to P388 tumor cells but spleen cells were not. While the C. parvum was effective against P388 in conventional mice, it was ineffective against P388 growing in athymic (nude) mice. Thus, the antitumor effect in this tumor system is T-cell dependent.

Drug-mediated immunogenic changes of virus-induced leukemia in vivo

LSTRA and RBL-5 lymphomas induced by Moloney and Rauscher leukemia viruses, respectively, were used to determine whether antigenically altered tumors induced by 5-(3,3-dimethyl-1-triazeno)-imidazole-4-carboxamide in vivo would retain their original antigenic properties and/or have new antigenic properties. The tumors became highly immunogenic in the syngeneic hosts after 4 to 8 transplant generations with drug treatment. Syngeneic mice could be protected against challenge with the parental tumor by presensitization with the drug-altered sublines while unrelated tumor lines were incapable of protecting them. The drug-altered subline of LSTRA was used for treatment of the LSTRA in conjunction with chemotherapy, and this immunochemotherapy produced significant increases in number of survivors and increases in median survival time compared to either treatment alone. Tolerance studies indicated that there are novel antigens and parental tumor antigens associated with the drug-treated sublines.

Naturally-occurring Sendai virus infection of athymic nude mice

Nude (nu/nu) mice, Balb/c-derived, responded to a naturally-occurring Sendai virus infection in a different manner than conventional mice. They developed a chronic debilitating disease and a persistent viral infection of the respiratory tract with intranuclear inclusion bodies in tracheal, bronchial and bronchiolar epithelial cells, laryngeal and tracheal glandular epithelium and in type I and II alveolar cells. The infection was identified by serologic and tissue culture studies, the mouse antibody production test and ultrastructural examination of pulmonary lesions. Phlebitis of pulmonary veins, suppurative rhinitis and otitis media accompanied the viral infection while some mice developed a secondary bronchopneumonia.

Inhibition of antilymphoma allograft response in normal and lethally irradiated mice by cyclophosphamide (NSC-26271) and isophosphamide (NSC-109724)

Cyclophosphamide and isophosphamide (an analog) were tested for their effect on the antilymphoma allograft reaction in normal and lethally irradiated mice. Both drugs were effective in abrogating the classic allograft response if given 1 or 3 days before the tumor challenge. While the drugs also inhibited the hemopoietic-histocompatibily response, they were effective when adminstered 7 days before challenge. It is suggested that the activity of various immunosuppressive agents could be compared for their effect on the hemopoietic-histocompatibility system to select the best agent for transplantation of bone marrow or bone marrow or bone marrow-derived cells. Drug toxicity, as well as the effect of the drugs on humoral response and DNA synthesis, was also compared. While isophosphamide was found to be less toxic than cyclophosphamide, the effect of humoral response and DNA synthesis was comparable.

Increased immunogenicity of two lymphoma lines after drug treatment of athymic (nude) mice

Highly immunogenic sublines of L1210 and LSTRA lymphomas were obtained from athymic (nude) mice treated with 4(5)-(3,3-dimethyl-1-triazeno)imidazole-5(4)carboxamide (DIC) in vivo. Conventional mice, compatible with the parent tumor, rejected the DIC-treated sublines and were relatively resistant to a subsequent challenge with the parent lines. The DIC-treated sublines were not rejected by athymic mice, which indicated that the transplantation resistance to these tumors in conventional mice was thymus-cell dependent. In addition, there was marginal or no increase of tumor-cell immunogenicity when the parent lines were passaged in nude mice without DIC treatment. This indicated that the DIC-dependent immunogenic changes in DIC-treated leukemic conventional mice could not be ascribed merely to protection by naturally occurring antigenic clones that resulted from DIC-induced immunodepression.

Effects of levamisole (NSC-177023) and tetramisole (NSC-102063) in experimental tumor systems

Levamisole and tetramisole had no antitumor effect against the following transplantable syngeneic murine tumors: L1210 leukemia, P388 leukemia, B16 melanoma, Madison 109 lung tumor, and Lewis lung carcinoma. In the Lewis lung carcinoma system there was no effect on primary tumor growth, metastasis, or survival. Tetramisole had a variable effect on the growth of rhabdomyosarcomas and the survival of BALB/c mice following intramuscular inoculation of Moloney sarcoma virus. In two experiments treatment with tetramisole either prior to or following inoculation of Moloney sarcoma virus increased the number of mice with tumor regression as opposed to progressive tumor growth, incrneased the number of long-term survivors, and prolonged the lifespan of mice that died of tumor. In two further tests neither levamisole nor tetramisole had an effect in this system. In mice immunosuppressed with cyclophosphamide prior to virus inoculation, there was not effect of treatment with levamisole or tetramisole.

Therapy in an intracerebral murine glioma model, using Bacillus Calmette-Guérin, neuraminidase-treated tumor cells, and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea

The s.c.-propagated murine glioma, GL-26, was established in tissue culture. The tissue culture line, with a doubling time of 36 hr, was used as the common source for all tumor cells. Suspensions of the tumor cells were transplanted intracerebrally in mice to produce an anaplastic ependymoblastoma. In vitro 51-Cr cytotoxicity assays did not detect any cellular immunity against GL-26 tumor cells in animals bearing either s.c. or i.c. tumors, indicating that the tumor itself is not highly immunogenic. Howeveer,significant cellular cytotoxicity was elicited in non-tumor-bearing animals by immunization with Vibrio cholerae neuramini-animals by immunization with Vibrio cholerae neuraminidase and mitomycin C-treated tumor cells plus complete Freund's adjuvant. In vivo therapy studies revealed significant increases in survival of animals preimmunized with V. cholerae neuraminidase- and mitomycin C-treated cells plus complete Freund's adjuvant. 1(2-Chloroethyl)-3-cyclohexyl-1-nitrosourea, when given i.p. on Day 3 or 12 after tumor challenge, also resulted in significant increases in survival. Furthermore, the effects of 1-(2-chloroethyl)- 3-cyclohexyl-1-nitrosourea and preimmunization were additive, with significanchloroethyl)-3-cyclohexyl-1-nitrosourea. In contrast to results reported for several extracranial tumor systems, immunotherapy, using either V.cholerae neuraminidase- and mitomycin-treated tumor cells, Bacillus Calmette-Guerin, or both, beginning 3 0r 4 days after tumor challenge, did not produce any significant increases in survival.

Uptake of 5-iododeoxyuridine as a measure of tumor growth and tumor inhibition

The DNA synthesis of tumor cells in spleen, lung and liver of mice bearing spontaneous or transplanted lymphomas or Lewis lung carcinoma was determined by measuring the uptake of 5-iododeoxyuridine labeled with iodine-125 (125IUdR). An in vitro uptake method was also developed to assess 125IUdR uptake of peripheral blood of leukemic animals. A direct relationship was found between isotope uptake values and the extent of neoplastic growth. The 125IUdR uptake method was found to be applicable to determination of inhibition of tumor growth in drug-treated animals and in pre-sensitized allogeneic hosts and to measurement of regression in non-sensitized allogeneic mice.

Immunity to Salmonella typhimurium infection: characterization of antigens in active protection by polyacrylamide gel electrophoresis

Immunity to challenge with Salmonella typhimurium (strain SR-11) was studied in NIH/NMRI Swiss mice. Viable organisms induced the best protection, but ribosomes were the best immunogen of the subcellular fractions. Antigens with lower concentrations of protein did not induce protection as well as antigens which had higher concentrations of protein. Acrylamide gel electrophoresis of the SR-11 subcellular components, fractionation, and differential staining of the gel columns indicated that the immunogen is a high-molecular-weight glycoprotein or mucopolysaccharide.